TRIPLEX, or XXX, is the secret classification assigned to material illicitly copied
from the diplomatic pouches of neutral embassies in wartime London.

TRIPLEX was acquired by a joint MI5 – SIS wartime operation to distract diplomatic
couriers overnight with male and female prostitutes on their journeys home and copy
the contents of the pouches. Invariably the couriers flew from Hull (to Stockholm)
or from Bristol (to Lisbon) but their civil aircraft would be delayed by mechanical
problems or adverse weather conditions, causing the pouches to be lodged overnight
with the airport police, thus allowing the target to reacquaint himself with the
attractive individual he first encountered hours earlier on the train. Once opened
and photographed by technicians, the diplomatic seals would be replaced by a team
of skilled craftsmen. The operation was conducted successfully throughout the war
without incident and was never compromised. There is no reason to believe that any
of the target diplomatic missions ever suspected their most confidential communications,
usually letters, reports, documents and other items too valuable to entrust to the
telegraph or wireless, had been accessed.

The operation was so secret that no mention of it has been made in any official history
of wartime British intelligence. However, full details are to be disclosed in Moscow
where the KGB archives have a collection of the TRPLEX product supplied by Anthony
Blunt while he was the senior MI5 officer supervising the operation.

This book, which takes its title from the operation, includes a selection of authentic
M5 and SIS documents never previously seen. This material amounts to the very first
evidence of precisely what Kim Philby, Anthony Blunt and John Cairncross betrayed
to their Soviet contacts.

Reviews

“The first complete report on the Cambridge Five that gives the reader the opportunity
to judge the extent of the damage done to the British... It will be greeted with
enthusiasm by specialists in intelligence history.”